1. Technical Field
The present invention relates generally to vehicle information systems and more particularly to a system which alerts the occupants of a vehicle to the presence of emergency vehicles, such as police cars, ambulances, fire fighting trucks or trains.
2. Discussion
Emergency vehicles are typically equipped with a plurality of flashing lights and loud sirens to alert motorists to their presence and yield the right of way to the emergency vehicle. While flashing lights and loud sirens are very effective in certain situations, such as at night on relatively straight roads away from intersections, there are times when these devices fail to effectively communicate the presence of the emergency vehicle to approaching motorists. This failure may result from the errors of an approaching motorist or from the characteristics of the area which the emergency vehicle is traveling.
For example, heavy overgrowth of trees and shrubs on the sides of an intersection will render the emergency vehicle difficult to see by approaching motorists, regardless of the time of day or the extent to which the approaching motorists are focusing on the task of driving. This problem is exacerbated by a motorist's operation of a vehicle audio system at high listening levels, as this tends to obscure the sound produced by the emergency vehicle's sirens.
Several systems for alerting motorists of approaching emergency vehicles have been developed but have not received widespread acceptance. These systems, such as the one disclosed in U.S. Pat. No. 4,238,778 which is hereby incorporated by reference as if fully set forth herein, alerts motorists to the presence of emergency vehicles if they are within a predetermined distance from one another, say for example, 100 yards. The emergency vehicle utilizes a VHF or UHF carrier signal which is transmitted to an omni-direction finding antenna coupled to the motorist's vehicle. This system does not inform the motorist of the relative direction of the emergency vehicle and requires a VHF or UHF receiver to receive the carrier signal.